Lithium mixed metal oxides, LiNi1-x-yCoxMnyO2, (LNCMO) are recognized as a suitable replacement for lithium cobalt oxide, LiCoO2, (LCO) as a cathode material in the secondary lithium ion batteries. Some of the reasons for the utilization of LNCMO include a lower price of the metals, increased availability of the metal raw materials, and tailorability of the electrochemical properties of LNCMO as compared to LCO. The preparation of LNCMO is, however, more challenging than that of LCO due to a higher probability of forming electrochemically inactive phases. The quality and uniformity of the cathode material is extremely important since it directly impacts battery performance. It has been observed that LNCMO properties and battery performance are more dependent on the properties of the mixed metal (NCM) precursor than in the case of the precursor for LCO. For example, metal composition, physical properties (e.g. particle size distribution, tap density) and morphology of the LNCMO particles are strongly derived from the manufactured precursor particles. Therefore, the preparation of the NCM precursor is a crucial step in preparing high quality LNCMO. Currently, NCM hydroxides (Ni1-x-yCoxMny(OH)2) are used as precursors for LNCMO. The key challenge in preparing mixed metal hydroxides for use as precursors for LNCMO is to obtain particles of high density. Typically, NCM hydroxides are prepared by precipitating the hydroxides from an aqueous metal containing solution with the alkaline hydroxide and ammonia. Alkaline hydroxide is used to control pH and the particle size. Ammonia is typically used as a complexing agent to inhibit the growth rate of the particles and to increase final the density of the particles. Further improvements in producing high density particles have been achieved using reducing agents which prevent the oxidation of the metals during precipitation.
It is also known that NCM oxyhydroxides (Ni1-x-yCoxMnyOOH) have been used as precursors for the preparation of LNCMO. In this approach, the precipitated precursor is subjected to a separate step which oxidizes the metals to the oxyhydroxide state prior to lithiation. This separate oxidation step can be done either chemically, through the addition of an oxidation agent, or thermally, with post heat treatment. The direct precipitation of oxyhydroxides is typically not preferred since the amount of impurities, for example sodium, increase due to possible lattice expansion and double salt precipitates. Therefore, the preferred approach is an additional oxidation step after the hydroxide precipitation to obtain an optimal precursor for cathode materials. Partly oxidized NCM hydroxides have also been proposed as precursors.
When considering the preparation of the NCM hydroxides and oxyhydroxides from an economical point of view, neither the addition of the reducing agent in the precipitation step nor the additional oxidation step is preferred.
Not withstanding the state of the art described herein, there is a need for further improvements in a mixed metal oxidized hydroxide precursor material and the production of such materials resulting in dense particles with high purity without the use of additional reducing agents or an oxidation step.